If I were Smith I'd have the batsmen accelerating throughout the afternoon session and look to declare at tea regardless of the score. They might push 250-300 if they get a move on, England could probably do with more delaying tactics. I can't believe Bopara has bowled 14 overs, or indeed Trott and Pietersen bowling overs - 19 overs for 72 runs I think, 4 an over with only occaisional threat.
If South Africa can win batting once they need to bowl England out for under 300-350 and have time to do so. Since they will use up valuable time getting that far in front I think they have to gamble they can take every chance, get everything go for them, and bowl England out for 270 or less.
Crux is they need to take 10 wickets to win, or bowl England out if someone is injured and can't bat, so need to have enough time to give them the best chance of doing so. Any batting South Africa do from here on in needs to be ODI speed. England will be as happy as they can be if still in the field post-tea, time is their potential saviour and enemy of the saffers
There's no way England should get bowled out for under 300 on this pitch but you never know.
While I agree with you in that they should declare around tea (maybe 5-10 overs later) I don't think they will give England more than 100 overs to bat. Modern captains are defensive like that and I just feel that Smith would that psychological advantage of 300.
Although Smith did declare around 280 in Australia, that was when he was young and brash and the loss would only serve to remind him that he would want atleast 300.
South Africa have only batted once, England would unlikely declare and try to bowl them out, and it is highly unlikely England would be bowled out for say 260-290 and South Africa not make any runs needed to win ie the chances of England being bowled out for under 300 and South Africa being bowled out for the 1st innings deficit or less are remote.
The odds of South Africa losing from here are astronomic
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I am somewhat bemused by using Bopara, going at over four an over when England surely want to slow the rate down. Unless he is taking 6-7 minutes per over, which at his pace I highly doubt, then he is just aiding the South African run rate. It is not like a wicket threat is going to slow them down much.
And people say Strauss is useless beyond his captaincy, his captaincy here is baffling.